The lift motor is physically jammed and not able to move.
Bad lower PCA.
Bad lift capacitor.
Bad lift motor winding.
Bad interconnect cable between upper and lower PCA.
Bad upper PCA.
Check the lift fuse from the lower PCA. Using an ohmmeter, the fuse should measure 1 ohm or less. If the reading is significantly high, replace the fuse. If the fuse is open, refer to steps 3 and 4 before continuing.
Disconnect the lift motor from the ramp (elliptical) or lift platform (treadmill). If the lift nut or lift tube is jammed against the motor housing, turn the lift tube or lift nut away from the motor housing. If the lift was jammed, refer to step 3 before continuing. Calibrate the lift motor per the proper procedure for the unit being serviced and reattach the lift motor to the ramp (elliptical) or lift platform (treadmill). NOTICE: You must find and repair the cause for the jammed lift. Only re-calibrating the lift motor will not solve the problem.
One of two modes can cause the lower PCA to fail. The lift switch could fail in an operating condition. If this happens the lift will move (either up or down) as soon as the unit powers up. The usual result is that the lift will be physically jammed as explained above, and probably also being the cause for the lift fuse to blow. The lift switch could also fail in an open condition. If this happened, the lift would not operate in one direction. If either of these conditions occurs the lower PCA needs to be replaced.
Most units have the lift capacitor mounted inside the lift motor, and others use external lift capacitors. This information applies to units with external lift capacitors. If the lift capacitor is shorted the lift fuse blows. Check the capacitor for a short using an ohmmeter. Disconnect the capacitor from the lift motor and test. A good capacitor reads in the millions of ohms. Replace the capacitor if the reading is significantly low. The capacitor can also fail in the open condition which would result in the lift motor trying to run but not having normal power. Test the capacitor by measuring AC voltage across it. A good capacitor will read AC peak voltage while an open capacitor reads AC RMS voltage.
When a lift motor winding is bad the lift will not operate in one or both directions depending upon the exact fault in the motor. Check the lift motor winding with an ohmmeter. AC lift motors have a split winding (3 wires) and DC lift motors will have a single winding. Both windings must be checked on an AC lift motor. Normal winding readings could vary anywhere between 1 and 60 ohms, depending on the lift motor being tested. See the proper service manual for the motor being tested.
Test unit with a known good interconnect cable. Replace the interconnect cable if necessary.
Test unit with a known good upper PCA. Replace the lower PCA if necessary.